Help to identify this A500 mood.

[Zetr0]

@CSXLAB

Personally I would modify the motherboard for a full 1MB of CHIP RAM.


What is CHIP RAM?
CHIP RAM means what is says, all the co-processing CHIP's ( Denise, Paula, Garry, CIA's and Blitter) can access this pool of RAM.

To do any native graphics on an Amiga, or native sound, all of this data has to go through CHIP RAM.  So the more CHIP RAM you have the better!

CHIP RAM is very precious on any Amiga, and most programs will make use of it, adding enhanced sound or features.


What is OTHERMEM ?
Now, OtherMem is just that - this is memory that cannot be directly used by the Amiga CHIP set.  OtherMem is short for Other Memory, this can be FAST MEMORY, which can only be used by the CPU or something that is known as SLOW (FAST) Memory.

The latter means that the memory is located on the motherboard and the CPU has to wait until its turn to fetch / put data in this memory area.  Back in the day this was a cheap way of adding memory to an Amiga, while it didn't improve processing performance it dose provide more RAM for the CPU to use.


Modifying you A500 for 1MB of CHIP RAM
So in your case I would remove the wires and put the GARY pin back in the socket.

I would then using the image I posted earlier, cut the track of JP2 (pins 2 and 3) and solder a bridge between pins 1 and 2.

I would then cut the trace between pins 2 and 3 of JP7A and thats it... you will then have 1MB of CHIP RAM.


CPU Accelerators and CPU FAST RAM
Once you get your accelerator or additional CPU Memory upgrade, this will appear as Other memory (FAST RAM).  FAST RAM alone will improve the performance of your CPU by nearly 33%.  Obviously an Accelerator will drastically improve performance considerably.

For example, an A600 is very much like an A500+, more often than not it is referred to as an SMT version of the A500+ with IDE.

Like an A500 the A600 can output about 0.54 MIPS of processing power, however with a simple ACA620 - this give you 3.3MIPS of processing power - about 600% increase!!

also the ACA620 will also provide up to 10.5MB of FAST RAM as well as a MAP ROM feature which I find is a most delicious cherry on the cake.


Sadly I do know the specification of the ACA500, my hope is that it includes a CPU and with some FAST RAM (and an IDE solution) this will be a MUST HAVE card for A500 / A500+ owners.... and to be fair even A2000 / A1000 owners too.

A500 RAM upgrade
Currently there are a couple of options available to use,  Kipper2k on http://www.amibay.com makes and sells 8MB FAST RAM adapters for approximately £40 - these are auto-config (which means plug and play) and it will boost your CPU performance by about 33%.  It will also give you lots of ram and you can create RAD disk's and store data to be buffered to CHIP ram.


I hope all this helps, to the non technical this stuff can get quite hairy quite quickly.

[desantii]

I thought most 8272s chips were the 8372A variant that address 1mb chip ram. Only the 8272 A/B or 8372B can address 2mb (both of these found in A3000s)

I had always thought 8371s were 512kb... we'll you learn something new everyday


1mb

I gots to reading..... .....  a lot =)


an OCS chip set is just that, it comprises of DENISE, and 8370 Agnus.

an ECS chip set seen on the A500 is a Super Denise and an 8375 Agnus, this is also an A600 as well.

Now this will bake your noodle a bit, what makes the chip set OCS or ECS is in fact the Denise.  If you have a Super Denise installed you essentially have an Enhanced Chipset, as you gain extra screen modes.

Agnus is just an (Address Generator Unit) - depending on what you have 8370, 8371, 72, 74 will determine the address it can generate, it also handles some aspects of video in regards to PAL / NTSC.

the 8370 can address 512KB of CHIP
the 8371 can address 1MB of CHIP
the 8372 can address 2MB of CHIP*
the 8375 can address 2MB of CHIP*

*I should mention that there are some revisions of 8372 and 8375 that can only address 1MB of CHIP - most notably a particular revision in the early rev5.3 A2000's

Sadly I don't think Commodore had any idea when it came to name convention and there are some crazy revisions within each iteration - its quite difficult to get a right answer as well as very easy to be complete confused.

Alexh, I believe a member here, he probably knows more about Agnii than anyone outside the designers at commodore to be honest

[mrknight]

Have a look at JP7A. It seems like it was cut open and then repaired again. Maybe someone was trying to do the 1MB CHIP RAM mod? I can't see properly on the photo but it seems that JP2 is untouched.

I've done the expansion RAM as FAST RAM mod myself. I also read about a mod somewhere that you can populate the mobo with 1MB (CHIP) and still use the 512KB expansion (as SLOW?) for a total of 1.5MB. I find that hard to belive. There are not enough address lines? Has anyone heard of this mod?

It's an interesting system you got there! I'd love to tinker with it=)

[csxlab]

Hey, then when I arrive home (Country I mean) I will check it.

And try to make all to 1mb

Thank you all for the reply's

[arttu80]

I gots to reading..... .....  a lot =)


an OCS chip set is just that, it comprises of DENISE, and 8370 Agnus.

an ECS chip set seen on the A500 is a Super Denise and an 8375 Agnus, this is also an A600 as well.

Now this will bake your noodle a bit, what makes the chip set OCS or ECS is in fact the Denise.  If you have a Super Denise installed you essentially have an Enhanced Chipset, as you gain extra screen modes.

Agnus is just an (Address Generator Unit) - depending on what you have 8370, 8371, 72, 74 will determine the address it can generate, it also handles some aspects of video in regards to PAL / NTSC.

the 8370 can address 512KB of CHIP
the 8371 can address 1MB of CHIP
the 8372 can address 2MB of CHIP*
the 8375 can address 2MB of CHIP*

*I should mention that there are some revisions of 8372 and 8375 that can only address 1MB of CHIP - most notably a particular revision in the early rev5.3 A2000's

Sadly I don't think Commodore had any idea when it came to name convention and there are some crazy revisions within each iteration - its quite difficult to get a right answer as well as very easy to be complete confused.

Alexh, I believe a member here, he probably knows more about Agnii than anyone outside the designers at commodore to be honest

I bow you for your replies regarding this topic. You really go for all the trouble explaining details for us whom aren't as enlightened. Great reading, thanks!